Split anode for bent gun ion trap cathode-ray tubes



July 31, 1951 E. POHLE 2,562,242

SPLIT ANODE FOR BENT GUN ION TRAP CATHCDE-RAY TUBES Filed June 6,1950 2 Sheets-Sheet l INVENTOR. ER/C POHL E E. POHLE July 31, 1 951 SPLIT ANODE FOR BENT GUN ION TRAP CATHODE-RAY TUBES 2 Sheets$heet 2 Filed June 6, 1950 Fig. 6'

INVENTOR. ERIC POHLE f w ATTORNEYS Patented July 31, 1951 SPLIT ANODE FOR BENT GUN ION TRAP CATHODE-RAY TUBES Eric Pohle, Clifton, N. J., assignor to Allen B. Du Mont Laboratories, Inc., Clifton, N. J., a

corporation of Delaware Application June 6, 1950, Serial No. 166,401

7 Claims. 1

This invention relates to cathode ray tubes having a single magnet ion trap and more parv ticularly to the anode tubes of this type,

In cathode ray tubes of the type described in copending application, Serial No. 129,260 by Kenneth Hoagland, assigned to applicants assignee, one of the most expensive elements of the electron gun and the one which is most difficult to fabricate is the bent metallic portion of the anode. This bent portion of the anode comprises two cylindrical sections having the axes thereof joined at an angle. These bent anodes commonly are fabricated from seamless nickel tubing, which is cut to length, held in a vise and bent to the proper angle. It is difflcult to bend this tubing without having it buckle, tear or spring back to a bend of smaller angle than is desired. -After the bending, it is necessary to swage one end of the tubing to form a large radius corona shield at the end proximal to the location of the second grid. At the other end of the anode, close tolerances on the size of the limiting aperture cup must be held in order to get the cup to fit snugly into the end of the anode tubing. These several factors plus the initial cost of the seamless tubing, which is considerably more expensive than fiat stock of the same thickness, combine to increase the cost of the complete bent anode structure.

Accordingly, one object of this invention is to provide an improved bent anode which avoids the enumerated difliculties by fabricating the structure from fiat stock.

Other objects are to provide a cheaper bent anode or a bent anode which allows easy assembly with the rest of the electrodes making up the electron gun.

- Other objects and advantages of the invention will be apparent after studying the following specification.

The invention, accordingly, is embodied in an electron gun structure including a bent anode fabricated from flat stock to give a structure formed of a plurality of sections; the sections being matched to form the tubular anode bent at the desired angle, and the invention is characterized by the features of construction, combinations of elements and arrangement of parts hereinafter to be described.

Referring to the drawings:

Figure 1 shows an electron gun comprising an anode constructed according to this invention;

Figure 2 shows a cross section of the anode in Figure 1;

Figure 3 shows a bottom view of the anode I in Figure 1;

Figure 4 illustrates the method of fabricating the anode;

Figure 5 shows an electron gun utilizing an anode constructed according to this invention;

Figure 6 is another view of the electron gun in Figure 5; and

Figure '7 illustrates the method of making the metal support posts in Figures 5 and 6.

The electron gun shown in Figure 1 comprises a base stem l0, lead in wires II, a grid structure l2, a cup shaped second grid l3, and a bent anode l4, all fastened in alignment to a pair of insulating support rods 15. Only one rod appears in Figure 1, for they are in the same plane and parallel. The control grid I2 is clamped to the support rods 15 by a pair of semi-cylindrical straps l9 and 2| with radial ends for matching them together and longitudinal fingers 22 and 23 extending therefrom. An insulating disc 24 which serves to carry the heater (not shown) is held in Place by the fingers 22 and 23.

The second grid 13 has a rolled or turned edge 26 forming a corona shield and is held in place facing the anode l4 by a groove 21 in the side wall of the cup [2. A corona shield 28 similar to 26 is held in place in the anode M by a groove 29.

The anode l4 comprises a straight cylindrical fore part 3| angularly displaced from the cylindrical hind part 82, which is coaxially aligned with the control grid l2 and the second grid I3. For this preferred embodiment of the invention, anode I4 is pressed or drawn in two matching sections 33 and 34 (Figure 3), which are mirror images of each other and are preferably joined together by integrally joining the abutting pairs of flanges 36 and 31 along the tops and bottoms thereof, respectively. To insure perfect matching of the two halves 33 and 34, they may be pressed -or drawn adjacent to each other on a sheet of flat metal stock to take advantage of the local homogeneity of the metal.

A limiting aperture cup 38 is attached to the front end of the anode l4 by welding around the periphery thereof, or, alternatively, the cup 38 may be held in place by the stiffening rib 39. A pair of centering springs 4| and 42 are snapped onto the outer edge of the cup 88 to hold the forward part of the gun in place in the cathode ray tube neck (not shown) and to make contact with the conductive coating (also not shown) commonly deposited on said neck.

The anode I4 is attached to the support rods ill by strap 43 having a transverse stiffening rib 44,

notch is preferably made sufficiently long to provide a slight allowance ior its exact placement.

The fitting of the corona shield 28 in the rib 29 is shown more clearly in Figure 2 along with the positioning of the limiting aperture cup 38. The flange 31 is shown in Figure 2 with the notch extending only part way in to the semi-cylindrical portion 34. Notch 49 is not extended back to the cylinder because in cutting it out, by stamping, a slight feather edge is inevitably left which contributes to irregularity-in the electric field in the anode.

The method of fabricating the anode is illustrated in Figure 4 where die 5| is shown holding the semi-cylindrical half section 34 in position for the punch 52 which will cut out the notch 49 from the flange 31. If the width of the punch 52 were extended laterally to cut the notch 49 all the way to the semi-cylindrical wall portion 34, it would be necessary to cut back the die 5| correspondingly leaving a sharp edge on the die which would be worn away very quickly by the cutting action. The result would be inaccurate mating of the punch and die and the resulting uneven edges on the notch would have a deleterious effect on the electrical field inside the anode 3|. One of the primary values of this type of ion trap cathode ray tube lies in the fact that the electron beam is always acted upon by substantially symmetrical electric fields, and this advantage would be lost if the field were distorted by burrs or misalignment of the electrodes.

The electron gun in Figure 5 is supported by a pair of glass rod supports H4, I I6, which lie in the same plane. Each of the electrodes; namely, the control grid II I, the second grid H2, and the anode I I3 is supported by two pairs of metal posts which are welded to the respective electrodes and inserted into the glass rods H4 and H6 when these latter two are in a molten state. The posts II'I holding the control grid III, the posts Ill holding the second grid H2 and the rear set of posts IIS on the anode II3 are welded substantially perpendicularly thereto and consequently present no unusual difiiculties. On the other hand the forward posts I2I are weldedsubstantially parallel to the posts H9 and so must be welded at an acute angle to the cylindrical wall of the fore part Ill of the anode II3 as shown in Figure 6.

Figure 7 illustrates a way of making these parts where the fore part IiII of the anode H3 is held by a clamp I22, which forms one. contact for the welding device I23. The other contact I24 .is clamped to the wire I26. When the wire I28 is pulled down into contact with the portion IN, the weld is formed at the point of contact and the wire I26 is cut off at a predetermined length above the point of contact to form the post I2I. The clamp I24 is then moved up the wire I26 and the machine is ready for a new half section I3I to be moved into place.

When the wire is forced into contact'with the cylindrical wall of the half section I3I, it is likely to skid down the slope, and to prevent this the wall of the half cylinder I3I may be deformed to a slight dent or level spot in the area surrounding the point of contact to form the area I32. The deformation may be of any desired form, but must not be great enough to distort the electrical field.

Although I have described this invention in relation to specific embodiments, they are to be interpreted as illustrations and it is understood the structure may be varied without departing from the spirit or scope of the invention.

What is claimed is: Y

1. A bent cylindrical anode for a cathode ray tube, said anode comprising two sections which are substantially mirror images of each other. each of said sections comprising a semi-cylindrical portion having the axis thereof formed of two lines intercepting at an angle, and lying in the plane intercepting said anode to form said sections, substantially planar radial flanges extending along the edges of said semi-cylindrical portions, said flanges on one of said sections abutting matching iianges on the matching section and being joined thereto.

2. A bent, metallic, cylindrical anode for a cathode ray tube, said anode comprising two sections which are substantially mirror images of each other, each of said sections comprising a semi-cylindrical portion having the axis thereof forming an angle, flanges extending from the two longitudinal edges of each of said sections, both of said flanges being substantially co-planar with the flanges of the matching section and being joined thereto, said anode being bent, to form said angle, in the plane of said flanges.

3. A bent, metallic, cylindrical anode for a cathode ray tube, said anode comprising two sections which match each other, each of said sections comprising a semicylindrical portion having its axis bent, to define an angle, in the plane of the longitudinal edges of said semicylindrical sections, flanges extending from the longitudinal edges of each of said sections, said flanges being substantially co-planar with the flanges of one section abutting matching flanges on the other section and being joined thereto, and an indented stiffening rib located transversely of the axes of said cylindrical anode proximal to one end thereof, with a corona shield havin a turned back rim and a radially extending rib matching the inner surface of said stiffening rib held thereby.

4. A bent, metallic, cylindrical anode for a cathode ray tube, said anode comprising two sections matching each other, each of said sections comprising a semicylindrical portion having the respective axis thereof bent to define an angle and lying in a plane intercepting said anode to form said sections, flanges extending from the "two longitudinal edges of each of said sections,

said flanges being substantially co-planar with the flanges of the matching section and being joined thereto, said anode being held by vitreous supports on either side thereof and being secured to said vitreous supports by a plurality of metal posts.

5. The anode structure in accordance with claim 4 in which each said section has a plurality of substantially flat portions in the curved side thereof, each of said posts being joined to said anode with respective ends of said posts abutting said flat portions.

6. The anode structure in accordance with claim 4 in which said posts are joined to said vitreous supports by molding one end in the side thereof to extend radially therefrom.

7. The anode structure in accordance wit claim 4 in which said vitreous supports lie in a 8 plane normal to the plane intercepting said (Number Name Date anode to form said sections. 2,432,037 O'Larte et a1 Dec. 2, 1947 ERIC POHLE. 2,436,264 OLarte et ai Feb. 17, 1948 I 2,436,265 Pohie et a1 Feb. 17, 1948 REFERENCES CITED 5 2,496,127 Kelar Jan. 31, 1950 The toliowing references are of record in the OTHER REFERENCES me of this patent The Negative-Ion Blemish in a Cathode-Ray UNITED STATES PATENTS Tube and Its Elimination," by R. M. Bowie, re- Number Name Dat 10 printed from the Proceedings of the Institute of 2,211,613 Bowie Aug.13, 1940 Radio Engineers, vol. 36, No. 12 (pages 1482- 2393957 OLarte et ai Jan. 15, 1946 1 December 1948, i 5,12. 1485).

2,429,824 Koch Oct. 28, 1947 

